Lost audio setting?

Hi, I'm looking for a setting that I know I saw previously that now seems to have gone missing in W10M. I have Cortana read me texts over Bluetooth only. Recently this has gotten annoying because there's no one button way to cancel it, without speaking, which sometimes I'd rather not do in certain settings. I know this used to be able to be turned off, but now I can't find it. I've got a 640 on release preview, build .321. Any ideas? Thanks.